1. Field of Invention
The present invention relates generally to passenger airbag modules mounted to instrument panels of vehicles and low risk deployment passenger airbag systems having top airbags and mid airbags which are respectively mounted to upper surfaces and front surfaces of instrument panels and, more particularly, to a low risk deployment passenger airbag system using a slim type passenger airbag module which is minimized in height and/or length, such that two passenger airbag modules, that is, a top airbag and a mid airbag, can be installed in a limited space defined by an instrument panel.
2. Description of the Related Art
Generally, airbag modules are installed in vehicles to protect drivers and passengers from major impact when a vehicle crash occurs. The airbags are classified into a driver airbag (DAB), which is installed in a steering handle of a driver's seat, and a passenger airbag (PAB), which is installed in an instrument panel across from a passenger seat, depending on the installation position thereof.
Particularly, the present invention relates to passenger airbags. The passenger airbags are classified into a top airbag, which is mounted to the horizontal upper surface of the instrument panel, and a mid airbag, which is mounted to a vertical surface of the instrument panel above a glove box, depending on an installation position thereof.
As shown in FIGS. 1a and 1b, a conventional passenger airbag system includes a single passenger airbag module, which is provided inside an upper or front surface of an instrument panel. As an example, FIG. 1a shows a conventional airbag system which includes a single top airbag module provided inside the upper surface of the instrument panel. FIG. 1b shows a conventional airbag system which includes a single mid airbag module provided inside the front surface of the instrument panel.
However, the conventional passenger airbag system having the single top or mid airbag is problematic in that, when a vehicle accident occurs, a cushion inflated towards a passenger seat strikes the head of an out-of-position occupant (OOP), such as a child or a small adult, thus resulting in a severe injury to his/her neck. In detail, in the case of FIG. 1a, when a vehicle accident occurs, as designated by the dotted lines, while the cushion 5 of the top airbag is deployed, a component force 6 that is deployed downwards is generated. The downward deployment component force 6 strikes the head of a child 1, who is adjacent to the instrument panel, in a downward direction, thus resulting in a severe injury to the neck of the child 1. In the case of FIG. 1b, while the airbag is deployed, a mid airbag cushion 9 generates a component force 10 that is deployed upwards. The upward deployment component force 10 strikes the jaw of an out-of-position child 1 in an upward direction, thus resulting in a severe injury to the neck of the child.
In an effort to overcome the above problems, recently, a low risk deployment passenger airbag system, in which two airbags are respectively mounted to the upper and front surfaces of the instrument panel, was developed. The low risk deployment passenger airbag system includes two airbag modules, that is, a top airbag module and a mid airbag module, which have small volumes and are respectively mounted to the upper surface and the front surface of the instrument panel. Thus, when the airbag is deployed, that is, when the top airbag and the mid airbag are deployed, they are operated in conjunction with each other, so that they are substantially horizontally deployed towards the head and the chest of the occupant, thus preventing the downward or upward deployment component force 6 or 10 resulting in an injury to the neck of the out-of-position child.
FIG. 2 shows a preferred embodiment of “LOW RISK DEPLOYMENT PASSENGER AIRBAG SYSTEM” proposed in PCT international publication No. WO 2005/120905, which was filed by the inventor of the present invention.
As shown in the drawing, the conventional low risk deployment passenger airbag system includes a top airbag, which is mounted to the upper surface of an instrument panel, and a mid airbag, which is mounted to the front surface of the instrument panel. In the conventional low risk deployment passenger airbag system having the above-mentioned construction, when a vehicle accident occurs, while the airbags are operated, a top airbag cushion 14 and a mid airbag cushion 16 comes into contact with each other and are operated in conjunction with each other, so that they are substantially horizontally deployed towards the head and the chest of an adult occupant 2 who is seated on a passenger seat (refer to the arrows designated by the reference numerals 17 and 18). Therefore, the neck of an out-of-position child or small adult 1 is prevented from being injured by the deployment of the airbag.
The present invention provides a slim type passenger airbag module for such low risk deployment passenger airbag systems. That is, in such a low risk deployment passenger airbag system, because the top airbag module and the mid airbag module must be mounted to the rear surface of the instrument panel in a limited space defined by the instrument panel, the installation area and space are insufficient. Therefore, in order to install two passenger airbag modules in the limited space of the instrument panel, a slim type passenger airbag module having a low height, that is, a small size, is required.
Furthermore, the present invention relates to an installation relationship between the top airbag and the mid airbag provided in the low risk deployment passenger airbag system, that is, it relates to the distance and angle between the two passenger airbag modules. In detail, the low risk deployment passenger airbag system must be constructed such that, when the airbag system is operated, the cushions of the top airbag and the mid airbag are horizontally deployed by contact, that is, interference therebetween. For this, the distance and angle between the top airbag and the mid airbag must be defined within appropriate ranges. Therefore, a slim type passenger airbag module that meets the above requirements is necessary.
FIGS. 3a and 3b are a perspective view and a sectional view showing an example of a conventional passenger airbag module. As shown in the drawings, the conventional passenger airbag module 100 includes a box-shaped airbag housing 20, a cylindrical inflator 31, which discharges deployment gas, a cushion 40, which is inflated towards a passenger seat using deployment gas, and a retainer 50, which supports the cushion 40.
In detail, the airbag housing 20 includes a cushion housing 21 and an inflator housing 22. The cushion 40, which is folded into a predetermined shape, is received in the cushion housing 21. The cylindrical inflator 31 is installed in the inflator housing 22. Here, the cushion housing 21 has an opening 25, through which the cushion 40 is inflated and is deployed by deployment gas towards the passenger seat, and a mounting flange 27, which has bolt holes and is integrally provided around the rim of the opening 25.
The inflator housing 22 has a cylindrical shape and is open at an upper end thereof. Coupling holes are formed through opposite ends of the inflator housing 22, so that the opposite ends of the cylindrical inflator 31 are inserted into and fastened to the coupling holes in the inflator housing 22. Furthermore, a bracket 64, which fastens the passenger airbag module to a tie bar 63, is mounted to the outer surface of the lower end of the inflator housing 22.
The cylindrical inflator 31 has a can structure. A gas discharge hole, through which deployment gas is discharged when a vehicle accident occurs, is formed at a predetermined position through the inflator 30. Furthermore, a bolt 32 is provided on one end of the cylindrical inflator 31, so that the cylindrical inflator 31 can be fastened to the end of the inflator housing 22 by tightening the bolt 32 into a nut 34. A connector 38 for electrical connection of the cylindrical inflator 31 is coupled to the other end of the cylindrical inflator 31.
The retainer 50 is fixed between the cushion housing 21 and the inflator housing 22, and fastens an inlet part of the cushion 40 to the cushion housing 21. In addition, a plurality of passing holes 51, through which deployment gas passes, and a plurality of bolt holes for the retainer 50 to the cushion housing 21 are formed through the retainer 50. The inlet part of the cushion 40 is fastened to the retainer 50 by coupling bolts.
Meanwhile, FIG. 4 is a schematic sectional view showing an instrument panel, to which a top airbag and a mid airbag are mounted. As shown in the drawing, the top airbag T is mounted to the upper surface of the instrument panel 65, and the mid airbag M is mounted to the front surface of the instrument panel 65. As such, the two passenger airbag modules T and M are installed in a limited installation area A, which is defined inside the rear surface of the instrument panel.
That is, the top airbag module T cannot be disposed in an area from a junction between a windshield glass G and the instrument panel 65 to a position spaced apart from the junction by a predetermined distance (L), in order to provide space for the rotation of an airbag door. Furthermore, because a glove box (GB) must be installed inside the front panel of the instrument panel 65, the mid airbag module M cannot be installed in that area. In addition, the top airbag module T and the mid airbag module M must be coupled to the tie bar 63, the passenger airbag modules T and M cannot be disposed below the tie bar 63. Therefore, the area for installation of the two passenger airbag modules T and M is limited to the shaded area A, which is defined in the dotted line. Furthermore, recently, vehicles, in which a concave depression is formed in the upper surface of the instrument panel or the front surface of the instrument panel is curved, are increasing in number. Thus, the area A for installation of the two passenger airbag modules T and M is further reduced.
Therefore, a slim type passenger airbag module, which makes it possible to install two airbag modules in the limited installation area A inside the instrument panel, is required. Furthermore, the slim type passenger airbag module, which can be applied to even the curved surface of the instrument panel, is required. In addition, the slim type passenger airbag module, which can meet requirements, such as the distance (D) between the top airbag T and the mid airbag M and inclination angles (α) and (θ) thereof, such that the cushions of the top airbag T and the mid airbag M can be horizontally deployed by operating in conjunction with each other, is required.